ABSTRACT Starr County is a poor Texas-Mexico border community that is 98% Mexican American and has the highest diabetes-related death rate in Texas. In previous Starr County studies, we tested interventions culturally tailored for Spanish-speaking Mexican Americans diagnosed with type 2 diabetes (T2DM). Each study participant was supported by a family member who also received program benefits; 70% of these supporters did not have diabetes. Compared to the control group, fewer non-diabetic supporters in the experimental group converted to diabetes by 12 months post study entry. The primary purpose of the proposed study is to test the effectiveness of our culturally tailored DSME intervention that will be adapted for preventing, or at least delaying, diabetes onset in Mexican Americans with prediabetes. The intervention will involve: 1) 12 2- hour weekly group educational sessions that emphasize eating and preparing healthy Mexican-American foods and increasing physical activity; 2) 15 2-hour bi-weekly/monthly support group sessions on problem solving the barriers to adopting healthier lifestyles; and 3) 3 booster sessions held at 6-month intervals. We will integrate aspects of the Diabetes Prevention Program, as well as motivational interviewing, and prior to intervention testing, we will conduct focus groups with key individuals in Starr County to confirm the strategy and obtain community support. Intervention effectiveness will be examined using a randomized, repeated measures, pretest/posttest control group design, with an ?enhanced? usual care control group. We will enroll 300 Mexican Americans with verified prediabetes from rosters of ongoing Starr County genetic studies. Groups of 10 will be constituted according to the area of the county in which people live; each group will be randomly assigned to experimental or control conditions. Growth curve analysis, using multilevel models, will be used to compare intervention effects on health outcomes over time. We hypothesize that participants in the experimental group, compared to the control group, will have better health outcomes (A1C, FBG, lipids, BP, physical activity, dietary intake, and anthropometric variables [BMI, waist circumference]) at 3, 6, 12, 24, and 36 months post baseline, as well as lower rates of converting to T2DM (OGTT) by 36 months. This study is a significant step in our plan to develop effective culturally tailored health programs for populations at high risk for T2DM.